The Environmental Protection Agency (EPA) has determined that leaking equipment, such as valves, pumps, and connectors, are the largest source of emissions of volatile organic compounds (VOCs) and volatile hazardous air pollutants (VHAPs) from petroleum refineries and chemical manufacturing facilities. A typical refinery or chemical plant can emit 600-700 tons per year of VOCs from leaking equipment. Accordingly, Leak detection and repair (LDAR) is an important part of reducing environmental contamination from such facilities.
The EPA has set forth standards and guidance on determining such leaks of VOCs and HAPs through a framework known as Method 21. This Method applies to, but is not limited to, valves, flanges and other connections, pumps and compressors, pressure relief devices, process drains, open-ended valves, pump and compressor seal system degassing vents, accumulator vessel vents, agitator seals, and access door seals. The Method establishes the type of instrumentation, equipment and supplies that can be used to monitor leaks; it also defines concentration standards for measuring emissions by equipment type; it defines how samples should be collected, tested and reported; it also establishes a protocol for quality control as well as criteria for auditing facilities and how they conduct LDAR.
LDAR for chemical processing plants, such as refineries, is typically performed by trained personnel. The trained personnel are tasked with physically inspecting and sampling a wide variety of valves, pipe flanges, compressors, etc. for leakage on a periodic basis. This typically includes taking measurements with a handheld chemical detector. Current LDAR programs are labor intensive, time consuming, and have been found by the Environmental Protection Agency (EPA) to rarely be properly implemented by plant operators. The proper implementation is something that the agency aggressively pursues with its oversight along with other state and local regulators.
The failure of plant operators to properly implement a LDAR program, in many cases, is due primarily to the overwhelming expense, record-keeping and complexity such programs require. The expense comes not only from the physical labor involved with visiting and testing each component for leakage, but with keeping track of acceptable leakage rates for the wide variety of components and varying standards that exist in a typical plant, such as a refinery.
For example, each type of valve may have its own acceptable leakage threshold. For each given type of valve, each size of that type of valve may have a different acceptable leakage threshold. Further, newer valves may have different acceptable leakage thresholds than older versions of the same valve. The same challenges exist with other components such as compressors, connectors, sampling ports, etc. Thus, the record keeping required to track all components and their respective acceptable leakage thresholds presents a significant challenge as plant components are replaced and/or updated. Leakage thresholds also depend on the type of analyzers used and their respective detection capability. As a result, matching analyzing equipment standards with those for which they are monitoring is extremely challenging when dealing with thousands and in some cases millions of components.
Therefore, the trained personnel must not only sample each component, but must also determine the acceptable leakage threshold for the sampled component based on documented standards and best practices. A significant risk of error is misidentification of a given component (and/or acceptable leakage threshold). Risk of error also exists when sampling, as human operators may misuse the equipment or the equipment may not be calibrated properly.
U.S. Pat. No. 7,176,793 discloses a detection device in the form of a strip for use in an enclosed container. The detection strip includes sensors of macro, meso or nanosize, all of which are referred to as nanosensors, for detecting materials that are harmful to human beings within an enclosed container and for transmitting a corresponding resonance frequency. One or more detection strips are initially placed within a container, depending on the size of the container. Other types of nanosensors including those that detect temperature, humidity, location and other conditions can also be part of the sensor array. The detection devices are designed to send off specific resonant frequency signals which can be detected by voltage changes and/or current changes which are correlated to any harmful material detected within the container. In some applications, sensors can be located in open air and can be configured to receive and sample a forced air flow. A serial number computer chip is provided for specifically identifying the detection device and transmitting a corresponding resonance frequency, which allows the container to be identified. A power source is provided for operating the detection strip. A hand-held or stationary monitor is provided for monitoring the container for any signals given off from the detection strips within the container. The detection devices are designed to give off a predetermined amount of background signal. In consequence, if no such signals are received, the container is highly suspect as being tampered with, allowing such a container to be quickly removed and its contents examined.